This invention is directed to a composite knob having a light pipe with a colored face used as an indicator and to a light pipe for incorporation in such a composite knob.
Light pipes formed of light transmitting plastic are used in instrument panels and knobs of various types installed in vehicles and vessels. It is desirable in many such applications to provide light pipes of specific colors, rather than using a clear light pipe. However, the light transmitting capabilities of a colored plastic light pipe are usually less than that of a light pipe made from a clear light transmitting plastic. Thus, the visibility or uniformity of brightness of a colored light pipe may be severely diminished if the light pipe is unusually long or if the light source is particularly weak. It should be understood that the term color as used herein can mean any color of the spectrum including white and that the color can vary in any degree of transparency from almost clear to translucent to near opaque. The term xe2x80x9cclearxe2x80x9d refers to a material having the appearance of clear glass.
Previous attempts to provide colored light pipes have included the application of colored films to the light emitting edges of clear light pipes. Such attempts have been unsatisfactory due to inadequate adhesion between the color film and the plastic of the light pipe, the poor wearing qualities of the color film and the labor intensive nature inherent in attaching a film to a light pipe.
Accordingly, an object of this invention is a light pipe which emits a colored light yet has light transmitting characteristics almost equivalent to those of a clear light pipe.
Another object of this invention is a light pipe comprised of two plastics, one clear and the other colored, which are securely fastened to each other.
Yet another object of this invention is a light pipe comprised of a clear plastic and a colored plastic in which one or both of the clear or colored plastics may be varied in light transmitting distance thickness to balance the light output of the light pipe according to the characteristics which are desired.
Still another object of this invention is a light pipe of two plastics, one clear and the other colored, in which the light transmitting distance across the colored plastic is much shorter than the light transmitting distance across the clear light transmitting plastic.
Still a further object of this invention is a knob incorporating any of the aforementioned light pipes which light pipe is visible from the exterior of the knob either through an opening formed in the knob or through a transparent or translucent window formed in the knob.
An additional object of this invention is a multi-part light pipe is formed by molding the parts of the light pipe in a multi-step process or by pre-manufacturing some of the parts and overmolding the other parts on the pre-manufactured parts.
Other objects of the invention will be found in the following specification, claims and drawings.